One of the key toxins produced by Bordetella pertussis, the pathogen responsible for the whooping cough, is its Adenylate Cyclase (CyaA). It was shown using a murine model that CyaA is required by the bacteria during the early phase of lung colonization (Goodwin and Weiss 1990). CyaA exhibits a unique mechanism of eukaryotic cell invasion by delivering in a dedicated fashion its catalytic domain into cell cytosol (Simsova, Sebo et al. 2004). Detoxified and recombinant CyaA used as a vaccine vector displays the exquisite ability to target CD11b/CD18-expressing antigen presenting cells (APC), as for example dendritic cells or Langerhans cells (Guermonprez et al. 2001). These residents APC are key innate cells in the initiation of antigen-specific T-cell responses following intradermal immunization approaches (Merad, Ginhoux et al. 2008). After specific binding to CD11b+ APC, CyaA carrying either a viral or tumour antigen can deliver its antigenic cargo in a dedicated manner (Preville, Ladant et al. 2005). Based on this unique technology, the Applicant has developed a clinical stage bivalent vaccine to cure HPV infected patients: ProCervix. ProCervix is a bivalent therapeutic vaccine prepared with a mixture of two different CyaA vaccines: one embedding the HPV16 E7 protein and the other one carrying the HPV18 E7 protein.
Indeed Human papillomavirus (HPV) infections are generally long lasting and a compromised host immune response can lead to the development of cervical cancer, especially with high-risk HPV such as HPV18 and HPV16. E7 oncoproteins of HPV are expressed all along the replicative cycle of the virus, thus making them chosen targets for T-cell mediated immunotherapy (Iwasaki 2010). B-cell mediated immunity to the viral capsid proteins has been shown to be sufficient for a prophylactic protection against HPV infection (Stanley 2010). However, innate and T-cell mediated immunities are critical to cure patients that are already infected by the virus (Frazer 2009). Besides, available HPV prophylactic vaccines are not efficient to treat already HPV-infected patients and to cure the disease, thus highlighting the importance to develop therapeutic vaccines that would elicit antigen-specific T cell responses against HPV antigens (Trimble and Frazer 2009).
Prophylactic vaccines are based on the development of a B-cell mediated immunity. By contrast, therapeutic vaccines aim to develop strong and robust pro-inflammatory CD4+ and CD8+ T cell responses for an efficient treatment of chronic infection (virus, bacteria, etc.) or of cancer (Bachmann and Jennings 2010). Many studies have described both in mouse model and in human patients that induction of an antigen-specific T cell immunity can be correlated with a protection against diseased cells, either infected cells or tumour cells (Pulendran, Li et al. 2010; Sallusto, Lanzavecchia et al. 2010). By measuring qualitative and quantitative aspects of the CD8+ T cell response induced post-therapeutic vaccination in tumour bearing mice, it is possible to predict the therapeutic outcome, i.e., the progression or the regression of the tumour in individual animals (Rosato, Zoso et al. 2006). After a successful therapeutic vaccination that leads to a complete elimination of diseased cells, a key aspect of this immunotherapy would be its potential to generate long-term memory T lymphocytes in order to protect the patient against secondary pathogen infection. Memory T lymphocytes can be classified in two main cellular subsets: TEM (Effector Memory) and TCM (Central Memory). TEM are the first memory T cells to be generated following the clonal contraction phase of the immune response which fit with the elimination of the pathogen. TEM are CD62L− CCR7− and preferentially reside in peripheral tissues, such as the skin, gut and lungs, where they provide a first line of defence for the host (Woodland and Kohlmeier 2009). Over time, TEM progressively differentiate towards a TCM phenotype: CD62L+ CCR7−. These T lymphocytes are preferentially localized in secondary lymphoid organs (Kaech, Hemby et al. 2002; Ahmed, Bevan et al. 2009). Nevertheless both TEM and TCM are found in the circulation. A critical aspect of CD8 memory response efficacy is the speed at which CD8+ memory T lymphocyte acquire lytic potential and thus eliminate infected cells upon a novel infection by the same pathogen in order to prevent the spread of the infection and in turn the associated disease development. It has been shown that mice, that have been able to clear Lymphocytic choriomeningitis virus (LCMV) acute infection via the development of antigen-specific CD8+ T-cell responses, also developed memory CD8+ T-cells able to rapidly eliminate infected cells (Barber et al., 2003).
Based on this knowledge, the inventors have extended the approach of therapeutic vaccination involving T cell mediated immune response to devise a new concept of therapeutic and prophylactic treatment of pathological condition(s) by way of combining the administration of active ingredients in a designed multivalent immunogenic composition involving vectorized epitopes.
In particular, the inventors designed multivalent therapeutic vaccines suitable to induce, in a single patient, an immunotherapeutic treatment against a diagnosed pathology while mounting a robust prophylactic response against antigens or epitopes that are not related to said treated pathology, and optionally mounting a protective and preventive response against the re-occurrence of said treated pathology.
Indeed, the use of CyaA-based multivalent therapeutic approaches highlights the potential of CyaA-carried polypeptide(s) to treat and possibly eradicate a determined infection or a cancer while providing in the same patient a strong immune response, preferably protective T-cell memory response, against targeted epitopes contained in said polypeptide(s) against which a prophylactic protection is sought, and optionally a protective and preventive response against the re-occurrence of said determined infection or cancer.